There is an industry need to improve the flow behavior of coating compositions comprising polyisocyanate compounds and hydroxyl-functional film-forming polymers, and the appearance of coatings formed from such coating compositions while maintaining other properties of the coating compositions and coatings. It has been found that non-volatile branched monoalcohols can provide the desired improvements. Particularly useful are long chain linear monoalcohols with 12 or more carbon atoms. Since these monoalcohols with 12 or more carbon atoms are generally solid at ambient temperature, their use in coatings compositions, is thought to be limited. Surprisingly, it has been found that some long chain non-volatile branched monoalcohols are suitable as an additive in coating compositions, in particular multi-component (at least two component) coating compositions. This results in coating compositions that have improved flow behavior and that produce coatings having improved appearance without an unacceptably adverse effect on other properties.
Coating compositions comprising a polyisocyanate and polyol are known from, for example, European Patent Application No. 0 219 131. This reference also discloses use of such coating compositions for various purposes, including the top coating of relatively heavy weight articles, such as vehicles, industrial machinery and building and construction machinery.
Fast setting, fast curing coating compositions using acrylic binders with a high Tg are mentioned, for example, in U.S. Pat. Nos. 5,741,880 and 5,759,631. The combination of a hard acrylic with a low viscosity polyol is mentioned in U.S. Pat. No. 5,286,782. To obtain low VOC coating compositions, fast evaporating solvents with low photochemical reactive solvents such as acetone, methylacetate and tertiary butylacetate can be added. Combining fast evaporating solvents with acrylic binders can result in poor flow and appearance. To improve flow and appearance, large amounts of low viscosity polyols are sometimes added, but they may cause slower curing and poor setting.
U.S. Pat. No. 4,235,766 discloses a coating composition comprising an organic polyhydroxy compound and an organic polyisocyanate. The coating composition additionally comprises 2-methyl-2-propanol and/or 2-methyl-2-butanol. These monoalcohols are volatile compounds. A disadvantage in using volatile compounds is that there is no control in how much of the compound is built into the coating after application of the coating composition and how much evaporates and contributes to the VOC of the coating composition.